linux-kernel - Re: [PATCH 0/2] virt: vmgenid: add generation counter

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Message-ID: <f1c6f809-ab10-fbe5-c9df-ce8c2de7b1ff@amazon.es>
Date:   Thu, 4 Aug 2022 15:33:36 +0200
From:   "Chalios, Babis" <bchalios@...zon.es>
To:     <linux-kernel@...r.kernel.org>
CC:     <tytso@....edu>, <Jason@...c4.com>, <dwmw@...zon.co.uk>,
        <graf@...zon.de>, <xmarcalx@...zon.co.uk>,
        <gregkh@...uxfoundation.org>, <bchalios@...zon.es>
Subject: Re: [PATCH 0/2] virt: vmgenid: add generation counter

On 3/8/22 17:21, bchalios@...zon.es wrote:
> From: Babis Chalios <bchalios@...zon.es>
>
> Linux recently added support for the VM Generation ID mechanism from
> Microsoft. The way this works currently is using the 128-bit blob
> provided by the vmgenid device to re-seed the RNG. While this works it
> has two main issues, (a) it is inherently racy due to the fact that it
> relies on a ACPI notification being delivered and handled and (b) the ID
> is unsuitable for exposing to user-space.
>
> This patch-set extends the vmgenid device to introduce a generation
> counter, a 32-bit counter which is different every time the unique ID
> changes. The addition to the original implementation in QEMU can be
> found here:
> https://lists.nongnu.org/archive/html/qemu-devel/2022-08/msg00524.html.
>
> The first patch re-works slightly the current vmgenid driver to add a
> function that parses an object from the vmgenid device and returns the
> physical address of the vmgenid data. The second patch uses that
> function to parse additionally the address of the generation counter
> from the vmgenid namespace. The counter is then exposed to the
> user-space through a misc-device which provides `read` and `mmap`
> interfaces.
>
> Babis Chalios (2):
>    virt: vmgenid: add helper function to parse ADDR
>    virt: vmgenid: add support for generation counter
>
>   Documentation/virt/vmgenid.rst | 120 ++++++++++++++++++++++++++
>   drivers/virt/vmgenid.c         | 151 ++++++++++++++++++++++++++++-----
>   2 files changed, 251 insertions(+), 20 deletions(-)
>   create mode 100644 Documentation/virt/vmgenid.rst
>

I am also CCing Michael from Microsoft since he was involved in the
last discussions regarding the Linux driver.

Cheers,
Babis
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